Method and system for a combined air-oil cooler and fuel-oil cooler heat exchanger

ABSTRACT

The heat exchanger assembly includes a first internal flow path configured to channel a flow of fluid to be cooled from a first inlet to a first outlet. The heat exchanger assembly also includes a second internal flow path configured to channel a flow of a first coolant from a first inlet to a first outlet. The heat exchanger assembly further includes an external flow path configured to receive a flow of a second coolant proximate a surface of the external flow path.

BACKGROUND

The field of the disclosure relates generally to gas turbine enginesand, more particularly, to a method and system for cooling oil in a gasturbine engine and maintaining a separation of a flammable coolant andan oxidizing coolant.

At least some known gas turbine engines include one or more oil coolingsystems that are configured to cool and lubricate components of gasturbine engines. Some gas turbine engines include an air-oil surfacecooler and/or a fuel-oil heat exchanger. Air-oil heat exchangersattached to the inner radial surface of the nacelle, and use fan air tocool the oil flowing through the air-oil heat exchanger. Air-oil surfacecoolers include fins protruding into the bypass airflow passageway thatexchange heat with the relatively cold fan air.

Fuel in aircraft engines is often heated to prevent water in the fuelfrom freezing and to improve combustion of the fuel. In some gas turbineengines relatively hot oil is used to heat the fuel. Air has typicallynot been used to heat the fuel. A leak in the fuel-oil heat exchangercould put fuel and oxygen in contact with each other inside the engine.Having separate air-oil and fuel-oil heat exchangers takes up valuablespace in the engine and adds weight to the engine.

BRIEF DESCRIPTION

In one aspect, a heat exchanger assembly includes a first internal flowpath configured to channel a flow of fluid to be cooled from a firstinlet to a first outlet. The heat exchanger assembly also includes asecond internal flow path configured to channel a flow of a firstcoolant from a first inlet to a first outlet. The heat exchangerassembly further includes an external flow path configured to receive aflow of a second coolant proximate a surface of the external flow path.

In another aspect, a method of cooling a working fluid includeschanneling one or more flows of a fluid to be cooled through a firstinternal flow path of a heat exchanger assembly. The method alsoincludes channeling one or more flows of cooling fluid to a secondinternal flow path of the heat exchanger assembly. The method furtherincludes channeling a flow of air proximate an exterior flow path of theheat exchanger. The heat exchanger includes a plurality of fin membersextending proximate the flow stream. The first internal flow path isthermally coupled to the second internal flow path and the plurality offin members.

In yet another aspect, a gas turbine engine includes a fan assemblyincluding a bypass duct. The gas turbine engine also includes a coreengine including a heat exchanger assembly. The heat exchanger assemblyalso includes a first internal flow path configured to channel a flow offluid to be cooled from a first inlet to a first outlet. The gas turbineengine further includes a second internal flow path coupled in thermalcommunication with the first internal flow path and configured tochannel a flow of a second coolant from a second inlet to a firstoutlet. The heat exchanger assembly also includes an external flow pathconfigured to receive a flow of air proximate a surface of the externalflow path.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIGS. 1-5 show example embodiments of the method and apparatus describedherein.

FIG. 1 is a schematic view of a gas turbine engine.

FIG. 2 is a schematic diagram of a combined air-oil and fuel-oil heatexchanger.

FIG. 3 is a schematic axial view of the combined air-oil and fuel-oilheat exchanger shown in FIG. 2.

FIG. 4 is a schematic radial view of the combined air-oil and fuel-oilheat exchanger shown in FIG. 2 configured in a countercurrent flowarrangement.

FIG. 5 is a schematic radial view of the combined air-oil and fuel-oilheat exchanger shown in FIG. 2 configured in a concurrent flowarrangement.

Although specific features of various embodiments may be shown in somedrawings and not in others, this is for convenience only. Any feature ofany drawing may be referenced and/or claimed in combination with anyfeature of any other drawing.

Unless otherwise indicated, the drawings provided herein are meant toillustrate features of embodiments of the disclosure. These features arebelieved to be applicable in a wide variety of systems comprising one ormore embodiments of the disclosure. As such, the drawings are not meantto include all conventional features known by those of ordinary skill inthe art to be required for the practice of the embodiments disclosedherein.

DETAILED DESCRIPTION

In the following specification and the claims, reference will be made toa number of terms, which shall be defined to have the followingmeanings.

The singular forms “a”, “an”, and “the” include plural references unlessthe context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where the event occurs and instances where it does not.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about”, “approximately”, and “substantially”, are notto be limited to the precise value specified. In at least someinstances, the approximating language may correspond to the precision ofan instrument for measuring the value. Here and throughout thespecification and claims, range limitations may be combined and/orinterchanged; such ranges are identified and include all the sub-rangescontained therein unless context or language indicates otherwise.

The following detailed description illustrates embodiments of thedisclosure by way of example and not by way of limitation. It iscontemplated that the disclosure has general application to a method andsystem for cooling oil in an aircraft engine.

Embodiments of the heat exchanger assembly described herein cool oil ina gas turbine engine. The heat exchanger assembly includes a combinedair-oil and fuel-oil heat exchanger located on an inner radial surfaceof a nacelle. The combined air-oil and fuel-oil heat exchanger includesa first flow path for channeling fuel through the heat exchanger, asecond flow path for channeling oil through the heat exchanger, and athird flow path for directing air proximate an outer finned surface ofthe heat exchanger. The heat exchanger cools the oil by exchanging heatwith fan air in the fan bypass duct and by exchanging heat with fuel. Inan exemplary embodiment, the heat exchanger is configured to cool oilwith fan air in the fan bypass duct and fuel simultaneously. The heatexchanger includes a plurality of fins disposed on the surface of theheat exchanger, which protrude into the fan bypass duct. The oil andfuel flow through one or more conduits included in the heat exchanger.The oil conduits are disposed within the heat exchangers between thesurface of the heat exchanger and the fuel conduits to maintain aseparation between the flow of fuel in the heat exchanger and the flowof air past the heat exchanger. In an exemplary embodiment, the oilconduits and fuel conduits are configured to flow in a countercurrentflow arrangement.

During operation, the heat exchangers receive relatively hot oil fromthe engine and relatively cool fuel from a fuel pump. Fan air in the fanbypass duct exchanges heat with the plurality of fins which exchangeheat with the oil. The fuel simultaneously exchanges heat with the oil.The oil is cooled by the fan air and the fuel at the same time in thesingle heat exchanger. The heat exchanger returns the heated fuel andcooled oil to the engine. In an alternative embodiment, the oil conduitsand fuel conduits are configured to flow in a co-flow arrangement. Inanother alternative embodiment, the heat exchangers are located on anouter radial surface of the engine.

The heat exchanger assemblies described herein offers advantages overknown methods of cooling oil in a gas turbine engine. More specifically,some known heat exchanger systems use separate heat exchanger assembliesto cool oil with air and fuel. Heat exchanger system described hereincombines the air and fuel cooling into a single heat exchanger assemblythat facilitates reducing the weight of the heat exchange system and ofthe aircraft engine. Placing oil conduits between the fuel conduits andthe fan bypass duct creates a buffer between the air and fuel.

FIG. 1 is a schematic cross-sectional view of a gas turbine engine inaccordance with an exemplary embodiment of the present disclosure. Inthe example embodiment, the gas turbine engine is a high-bypass turbofanjet engine 110, referred to herein as “turbofan engine 110.” As shown inFIG. 1, turbofan engine 110 defines an axial direction A (extendingparallel to a longitudinal centerline 112 provided for reference) and aradial direction R. In general, turbofan 110 includes a fan section 114and a core turbine engine 116 disposed downstream from fan section 114.

Exemplary core turbine engine 116 depicted generally includes asubstantially tubular outer casing 118 that defines an annular inlet120. Outer casing 118 encases, in serial flow relationship, a compressorsection including a booster or low pressure (LP) compressor 122 and ahigh pressure (HP) compressor 124; a combustion section 126; a turbinesection including a high pressure (HP) turbine 128 and a low pressure(LP) turbine 130; and a jet exhaust nozzle section 132. A high pressure(HP) shaft or spool 134 drivingly connects HP turbine 128 to HPcompressor 124. A low pressure (LP) shaft or spool 136 drivinglyconnects LP turbine 130 to LP compressor 122. The compressor section,combustion section 126, turbine section, and nozzle section 132 togetherdefine a core air flow path 137.

For the embodiment depicted, fan section 114 includes a variable pitchfan 138 having a plurality of fan blades 140 coupled to a disk 142 in aspaced apart manner. As depicted, fan blades 140 extend outwardly fromdisk 142 generally along radial direction R. Each fan blade 140 isrotatable relative to disk 142 about a pitch axis P by virtue of fanblades 140 being operatively coupled to a suitable pitch changemechanism 144 configured to collectively vary the pitch of fan blades140 in unison. Fan blades 140, disk 142, and pitch change mechanism 144are together rotatable about longitudinal axis 112 by LP shaft 136across a power gear box 146. Power gear box 146 includes a plurality ofgears for adjusting the rotational speed of fan 138 relative to LP shaft136 to a more efficient rotational fan speed.

Referring still to the exemplary embodiment of FIG. 1, disk 142 iscovered by rotatable front hub 148 aerodynamically contoured to promotean airflow through plurality of fan blades 140. Additionally, exemplaryfan section 114 includes an annular fan casing or outer nacelle 150 thatcircumferentially surrounds fan 138 and/or at least a portion of coreturbine engine 116. Nacelle 150 includes an inner radial surface 151. Itshould be appreciated that nacelle 150 may be configured to be supportedrelative to core turbine engine 116 by a plurality ofcircumferentially-spaced outlet guide vanes 152. Moreover, a downstreamsection 154 of nacelle 150 may extend over an outer portion of coreturbine engine 116 so as to define a bypass airflow passage 156therebetween. A plurality of combined air-oil cooler and fuel-oil coolerheat exchangers 157 is disposed on inner radial surface 151 of nacelle150 in bypass airflow passage 156. In an alternative embodiment, aplurality of combined air-oil cooler and fuel-oil cooler heat exchangers159 is disposed on outer radial surface 161 of outer casing 118 inbypass airflow passage 156.

During operation of turbofan engine 110, a volume of air 158 entersturbofan 110 through an associated inlet 160 of nacelle 150 and/or fansection 114. As volume of air 158 passes across fan blades 140, a firstportion of air 158 as indicated by arrows 162 is directed or routed intobypass airflow passage 156 and a second portion of air 158 as indicatedby arrow 164 is directed or routed into core air flow path 137, or morespecifically into LP compressor 122. The ratio between first portion ofair 162 and second portion of air 164 is commonly known as a bypassratio. The pressure of second portion of air 164 is then increased as itis routed through HP compressor 124 and into combustion section 126,where it is mixed with fuel and burned to provide combustion gases 166.First portion of air 162 exchanges heat with combined air-oil cooler andfuel-oil cooler heat exchangers 157 disposed on inner radial surface 151of nacelle 150 in bypass airflow passage 156. In an alternativeembodiment, first portion of air 162 exchanges heat with combinedair-oil cooler and fuel-oil cooler heat exchangers 159 disposed on outerradial surface 161 of outer casing 118 in bypass airflow passage 156.

Combustion gases 166 are routed through HP turbine 128 where a portionof thermal and/or kinetic energy from combustion gases 166 is extractedvia sequential stages of HP turbine stator vanes 168 that are coupled toouter casing 118 and HP turbine rotor blades 170 that are coupled to HPshaft or spool 134, thus causing HP shaft or spool 134 to rotate,thereby supporting operation of HP compressor 124. Combustion gases 166are then routed through LP turbine 130 where a second portion of thermaland kinetic energy is extracted from combustion gases 166 via sequentialstages of LP turbine stator vanes 172 that are coupled to outer casing118 and LP turbine rotor blades 174 that are coupled to LP shaft orspool 136, thus causing LP shaft or spool 136 to rotate, therebysupporting operation of LP compressor 122 and/or rotation of fan 138.

Combustion gases 166 are subsequently routed through jet exhaust nozzlesection 132 of core turbine engine 116 to provide propulsive thrust.Simultaneously, the pressure of first portion of air 162 issubstantially increased as first portion of air 162 is routed throughbypass airflow passage 156 before it is exhausted from a fan nozzleexhaust section 176 of turbofan 110, also providing propulsive thrust.HP turbine 128, LP turbine 130, and jet exhaust nozzle section 132 atleast partially define a hot gas path 178 for routing combustion gases166 through core turbine engine 116.

It should be appreciated, however, that exemplary turbofan engine 110depicted in FIG. 1 is by way of example only, and that in otherexemplary embodiments, turbofan engine 110 may have any other suitableconfiguration. It should also be appreciated, that in still otherexemplary embodiments, aspects of the present disclosure may beincorporated into any other suitable gas turbine engine. For example, inother exemplary embodiments, aspects of the present disclosure may beincorporated into, e.g., a turboprop engine.

FIG. 2 is a schematic diagram of a heat exchanger assembly 200. In theexample embodiment, the heat exchanger assembly 200 is a combinedair-oil and fuel-oil heat exchanger. Heat exchanger assembly 200includes a surface 202 disposed on inner radial surface 151 (shown inFIG. 1). Heat exchanger assembly 200 also includes a plurality of finmembers 204 disposed on surface 202 and extending into bypass airflowpassage 156 (shown in FIG. 1). A plurality of first internal flow paths206 is disposed within heat exchanger assembly 200. Heat exchangerassembly 200 includes a plurality of first internal flow paths inlets208 configured to receive oil and coupled in flow communication withfirst internal flow paths 206. Heat exchanger assembly 200 also includesa plurality of first internal flow paths outlets 210 coupled in flowcommunication with first internal flow paths 206. A plurality of secondinternal flow paths 212 is disposed within heat exchanger assembly 200.Heat exchanger assembly 200 includes a plurality of second internal flowpath inlets 214 configured to receive fuel and that are coupled in flowcommunication with second internal flow paths 212. Heat exchangerassembly 200 also includes a plurality of second internal flow pathsoutlets 216 coupled in flow communication with second internal flowpaths 212. First internal flow path 206 is disposed radially inward withrespect to second internal flow path 212.

During operation, first portion of air 162 (shown in FIG. 1) in bypassairflow passage 156 (shown in FIG. 1) is configured to flow proximate tosurface 202 and configured to exchange heat with fin members 204. Firstinternal flow paths inlets 208 are configured to receive a flow of oil.First internal flow paths inlets 208 are configured to deliver the flowof oil to first internal flow paths 206. Oil in first internal flowpaths 206 is configured to exchange heat with fuel in second internalflow paths 212 and with first portion of air 162 (shown in FIG. 1) inbypass airflow passage 156 (shown in FIG. 1). First internal flow paths206 are configured to deliver oil to first internal flow paths outlets210 which are configured to deliver oil to core turbine engine 116(shown in FIG. 1).

Second internal flow paths inlets 214 are configured to receive a flowof fuel. Second internal flow path inlets 214 are configured to channelthe flow of fuel to first internal flow paths 212. Fuel in secondinternal flow paths 212 is configured to exchange heat with oil in firstinternal flow path 206. Second internal flow paths 212 are configured todeliver fuel to second internal flow paths outlets 216 which areconfigured to channel fuel to core turbine engine 116 (shown in FIG. 1).

FIG. 3 is a schematic axial view of combined air-oil and fuel-oil heatexchanger assembly 200 shown in FIG. 2. First internal flow path 206 isdisposed within heat exchanger assembly 200 between surface 202 andsecond internal flow path 212. In the event that fuel leaks from secondinternal flow path 212 toward surface 202, first internal flow path 206acts as a buffer to intercept leaking fuel before it reaches bypassairflow passage 156 (shown in FIG. 1).

FIG. 4 is a schematic radial view of combined air-oil and fuel-oil heatexchanger assembly 200 shown in FIG. 2 configured in a countercurrentflow arrangement. First internal flow path 206 is configured flow oil ina first direction as indicated by arrow 402. Second internal flow path212 is configured to flow fuel in a second direction as indicated byarrow 404. First direction 402 is opposite second direction 404.

FIG. 5 is a schematic radial view of combined air-oil and fuel-oil heatexchanger assembly 200 shown in FIG. 2 configured in a co-current flowarrangement. First internal flow path 206 is configured to channel oilin a first direction as indicated by arrow 502. Second internal flowpath 212 is configured to channel fuel in a second direction asindicated by arrow 504. First direction 502 is in substantially the samedirection as second direction 504.

In an alternative embodiment, combined air-oil and fuel-oil heatexchanger assembly 200 is disposed on outer radial surface 161 of outercasing 118 in bypass airflow passage 156.

The above-described heat exchange assemblies provide an efficient methodfor cooling oil in a gas turbine engine. Specifically, theabove-described heat exchange system combines an air-oil cooler and afuel-oil cooler into a single heat exchanger. Combining the air-oilcooler and fuel-oil cooler into a single heat exchanger reduces thenumber of parts in an aircraft engine and reduces the complexity of theengine. As such, combining the air-oil cooler and fuel-oil cooler into asingle heat exchanger reduces the weight of the engine. Additionally,locating the oil conduits between the fuel conduits and the bypassairflow passage creates a barrier between the fuel and the air. Creatinga barrier between the air and the fuel reduces the likelihood thateither will leak to the other.

Exemplary embodiments of combined air-oil cooler and fuel-oil coolersurface cooler are described above in detail. The combined air-oilcooler and fuel-oil cooler surface cooler, and methods of operating suchsystems and devices are not limited to the specific embodimentsdescribed herein, but rather, components of systems and/or steps of themethods may be utilized independently and separately from othercomponents and/or steps described herein. For example, the methods mayalso be used in combination with other systems requiring oil cooling,and are not limited to practice with only the systems and methods asdescribed herein. Rather, the exemplary embodiment can be implementedand utilized in connection with many other machinery applications thatare currently configured to receive and accept combined air-oil coolerand fuel-oil cooler surface cooler.

Example methods and apparatus for cooling oil with air and fuel aredescribed above in detail. The apparatus illustrated is not limited tothe specific embodiments described herein, but rather, components ofeach may be utilized independently and separately from other componentsdescribed herein. Each system component can also be used in combinationwith other system components.

This written description uses examples to describe the disclosure,including the best mode, and also to enable any person skilled in theart to practice the disclosure, including making and using any devicesor systems and performing any incorporated methods. The patentable scopeof the disclosure is defined by the claims, and may include otherexamples that occur to those skilled in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal languages of the claims.

What is claimed is:
 1. A heat exchanger assembly comprising: a firstinternal flow path configured to channel a flow of fluid to be cooledfrom a first inlet to a first outlet; a second internal flow pathconfigured to channel a flow of a first coolant from a first inlet to afirst outlet; and an external flow path configured to receive a flow ofa second coolant proximate a surface of said external flow path.
 2. Thesystem of claim 1, wherein said first internal flow path and said secondinternal flow path are countercurrent flow.
 3. The system of claim 1,wherein said external flow path comprises a plurality of metallic fins.4. The system of claim 1, wherein said second internal flow path ispositioned between said first internal flow path and said external flowpath.
 5. The system of claim 1, wherein said second internal flow pathprovides a buffer between said first internal flow path and saidexternal flow path.
 6. The system of claim 1, wherein said flow of fluidto be cooled comprises oil.
 7. The system of claim 1, wherein said firstcoolant comprises fuel.
 8. The system of claim 1, wherein said secondcoolant comprises air.
 9. A method of cooling a fluid using a three pathheat exchanger, said method comprising: channeling one or more flows ofa fluid to be cooled through a first internal flow path of a heatexchanger assembly; channeling one or more flows of cooling fluid asecond internal flow path of the heat exchanger assembly; and channelinga flow of air proximate an exterior flow path of the heat exchanger, theheat exchanger including a plurality of fin members extending proximatethe flow stream, the first internal flow path is thermally coupled tothe second internal flow path and the plurality of fin members.
 10. Themethod of claim 9, wherein channeling one or more flows of fluid to becooled to a first internal flow path of a heat exchanger assemblycomprises channeling one or more flows of oil to the first internal flowpath of a heat exchanger assembly.
 11. The method of claim 9, whereinchanneling one or more flows of cooling fluid a second internal flowpath of the heat exchanger assembly comprises channeling one or moreflows of fuel to the second internal flow path of the heat exchangerassembly.
 12. The method of claim 9, wherein channeling a flow of airproximate an exterior flow path of the heat exchanger compriseschanneling a flow of fan exhaust air proximate a plurality of finmembers extending into the flow of air.
 13. A gas turbine enginecomprising: a fan assembly comprising a bypass duct; and a core enginecomprising a heat exchanger assembly that includes: a first internalflow path configured to channel a flow of fluid to be cooled from afirst inlet to a first outlet; a second internal flow path coupled inthermal communication with said first internal flow path and configuredto channel a flow of a second coolant from a second inlet to a firstoutlet; and an external flow path configured to receive a flow of airproximate a surface of said external flow path.
 14. The gas turbineengine of claim 13, wherein said first internal flow path and saidsecond internal flow path are countercurrent flow.
 15. The gas turbineengine of claim 13, wherein said external flow path comprises aplurality of metallic fins.
 16. The gas turbine engine of claim 13,wherein said second internal flow path is positioned between said firstinternal flow path and said external flow path.
 17. The gas turbineengine of claim 13, wherein said second internal flow path provides abuffer between said first internal flow path and said external flowpath.
 18. The gas turbine engine of claim 13, wherein said heatexchanger assembly is disposed on a radially outer surface of said coreengine.
 19. The gas turbine engine of claim 13 further comprising astationary annular casing at least partially surrounding said coreengine, wherein said heat exchanger assembly is disposed on a radiallyinner surface of said annular casing.
 20. The gas turbine engine ofclaim 13, wherein said flow of fluid to be cooled comprises oil.